This invention relates to the field of polymer sheet or film, particularly thermotropic liquid crystalline polymer ("LCP") sheet having one or more LCP components.
A variety of thermotropic liquid crystal polymers and films made therefrom are known in the art. For example, U.S. Pat. No. 4,161,470 discloses a polyester of 6-hydroxy-2-naphthoic acid and p-hydroxy benzoic acid capable of undergoing melt processing, U.S. Pat. No. 4,184,996 discloses melt processible thermotropic wholly aromatic polyesters, and U.S. Pat. No. 4,279,803 discloses a polyester of phenyl-4-hydroxybenzoic and 4-hydroxybenzoic acid and/or 6-hydroxy-2-naphthoic acid.
Other patents disclosing LCPs include U.S. Pat. Nos. 3,991,013, 3,991,014, 4,057,597, 4,066,620, 4,067,852, 4,075,262, 4,083,829, 4,093,595, 4,118,372, 4,130,545, 4,219,461, 4,267,289, 4,276,397, 4,330,457, 4,339,375, 4,341,688, 4,351,917, 4,351,918, 4,355,132, 4,355,133, 4,371,660, 4,375,530, 4,460,735, 4,460,736, 4,473,682, 4,489,190, 4,581,443, 4,671,969, 4,673,591, 4,726,998, 4,752,643, 4,770,777, 4,772,421, 4,857,255, 4,898,924, and 4,913,867.
The disclosures of all the aforementioned patents are herein incorporated by reference.
Due to the particular molecular structure of thermotropic liquid crystal polymers, LCP film can be molecularly oriented in the melt phase, uniaxially, biaxially, or otherwise. After the extruded LCP cools and solidifies, the molecular orientation is maintained. When the orientation is uniaxial, this results in a film having anisotropic properties, such as enhanced mechanical properties in the direction(s) of orientation (e.g. high strength and stiffness). However, the film's properties in other directions are often much poorer.
In producing LCP film/sheet, molded articles, and fibers, there is a certain amount of scrap LCP left over after processing. Due to the expensive nature of this material, and in keeping with modern environmental theory, it is desirable to recycle this material. Recycling scrap is especially difficult if the scrap contains a mixture of materials. For example, in processes for producing the coextruded LCP film described in pending U.S. Pat. application Ser. No. 800,774 filed Nov. 27, 1991, now U.S. Pat. No. 5,248,530 the disclosure of which is herein incorporated by reference, one would expect the scrap to contain at least two liquid crystal polymer components.